Flexible elastomeric sleeves are used in various types of fluid pressure systems and devices such as air springs which are used as both vibration isolators and actuators. These pneumatic devices or air springs as they are commonly referred to are used for a variety of applications. One particular application is providing cushioning or vibration isolation between movable parts of a vehicle to absorb shock loads impressed on the vehicle axis by the wheels striking an object on the road or entering into a depression. Many of these devices also are used as actuators to provide movement between two parts of a machine or piece of equipment.
Most of these air springs have annular beads at the ends of a flexible elastomeric sleeve which forms a fluid pressure chamber, which beads are clamped or crimped onto rigid end members or end plates. The end members are mounted on spaced portions of a vehicle or other equipment on which the air springs are mounted. Currently, these beads are internally reinforced with high strength wire which is wound into a continuous diameter or ring and then molded within the ends of the flexible sleeves to assist in maintaining the sleeve beads in an airtight sealing relationship with the end members. These bands are also molded into a midpoint of the sleeves to form a girdle hoop therefor for certain applications.
Although these prior steel band or wire reinforced beads and girdle hoops are satisfactory, they increase the weight of the air spring and increase the cost of the device due to the expense of the wire. Also, additional manufacturing costs are required for forming the wire into an annular band prior to molding it within the ends or midsection of the elastomeric sleeve.
Some examples of prior art devices using a reinforced bead are shown in the following patents.
U.S. Pat. No. 3,897,941 shows a type of flexible resilient tubular member used in a fluid pressure system having a reinforced bead in which the reinforcement is an annular metal band located at each end of the resilient member.
U.S. Pat. No. 3,237,674 discloses a reinforcing bead ring used as part of a bead assembly for pneumatic tires in which the bead assembly has a resin-impregnated glass fiber material combined with an epoxy resin matrix and molded into a hoop-like configuration which is molded within the bead area of a pneumatic tire.
U.S. Pat. No. 4,168,193 discloses a tire bead ring configuration in which a generally annular ring is held in place within a filled rubber compound which has been injection molded to provide reinforcement of a tire bead. The bead core is indicated as being strands of wire or fiberglass.
U.S. Pat. No. 4,231,408 discloses a tire having a plurality of elongated reinforcing members mounted in the sidewall area of the tire which are formed as a single unit of a wire reinforced rubber tape, rayon, nylon, polyester, aramid, fiberglass, steel, bronze coated steel, or the like.
Japanese Pat. No. 55-127210 discloses a bead wire formed with a circular cross sectional configuration or a six-sided configuration.
Although the prior bead reinforcements and girdle hoops formed of wire have proved satisfactory, they increase the cost of the fluid pressure device and the weight thereof. Attempts have been made to form the bead of a fiber reinforced synthetic material but such reinforcements have been found to be unsatisfactory due to the brittleness and stiffness of the bead ring preventing it from flexing sufficiently with the movement of the fluid pressure device.
Therefore the need has existed for a reinforcing ring used as a bead reinforcement or girdle hoop which is less expensive to manufacture and lighterweight than existing metal bands, and which is sufficiently flexible to move repeatedly with the flexible elastomeric sleeve without breaking.